A new study led by the University College London (UCL) has found that individuals living with long Covid who suffer from loss of smell (anosmia) have reduced brain activity and impaired communication between the orbitofrontal cortex and the prefrontal cortex, two areas of the brain which process important smell information.
The findings suggest that smell loss caused by long Covid is associated with a change in the brain that stops smells from being processed properly.
The experts used MRI scans to compare the brain activity of individuals with long Covid experiencing anosmia, those whose smell returned after their Covid infection, and people who never tested positive for Covid.
The analysis revealed that, although the brain impairment of people with long Covid suffering from loss of smell seemed quite persistent, in those who regained their sense of smell after Covid, the connection between the two brain areas was not impaired. This finding suggests that it may be possible to retrain the brain to recover its sense of smell.
“Persistent loss of smell is just one way long Covid is still impacting people’s quality of life – smell is something we take for granted, but it guides us in lots of ways and is closely tied to our overall wellbeing,” said lead author Jed Wingrove, a neuroimaging scientist and data analyst at UCL. “Our study gives reassurance that, for the majority of people whose sense of smell comes back, there are no permanent changes to brain activity.”
“Our findings highlight the impact Covid-19 is having on brain function. They raise the intriguing possibility that olfactory training – that is, retraining the brain to process different scents – could help the brain to recover lost pathways, and help people with long Covid recover their sense of smell,” added joint senior author Claudia Wheeler-Kingshott, a professor of Magnetic Resonance Physics at the UCL Institute of Neurology.
The researchers also discovered that the brains of people with long Covid smell loss might be compensating for this lost sensorial capacity by creating neuronal connections with other sensory regions of the brain, such as the visual cortex, suggesting that the neurons which would normally process smell are still there, but are functioning in a different way.
The study is published in the journal EClinicalMedicine.